‘Ill-defined and incomprehensible to contemporaries': these are two of the charges scholarship has levelled at the papal protection privilege for crusaders. Major innovations in this field have been attributed to Innocent III (1198-1216), yet many of these ideas can be identified as having developed much earlier. This thesis will demonstrate the profound originality of the protection initiated by Urban II in 1095, and discuss the role of the protection in recruitment as an added attraction or, at least, as a way for the pope to negate obstacles to taking the cross. Under Eugenius III (1145-53) this privilege took on a new formula that dominated papal missives beyond Innocent III's pontificate. In essence, crusaders were differentiated from pilgrims, and that protection sharply delineated crusaders' wives, families and possessions from those of the men-at-arms who did not take the cross. During the Second Crusade (1145-49), the metaphor of the two swords of government took on a new centrality within the crusading context. This connection between secular and spiritual authority has not received adequate attention from scholars. Protected status is the starting point of the discussion of papal and secular guardianship over the crusaders' lands and possessions. Crusaders and those remaining in the West were well aware of their status from the outset. This secular experience is determined through detailed discussion of the charters issued by crusade regents. The crusades have been interpreted as ‘windows of opportunity' for wives otherwise excluded from politics, however demonstrably the women chosen for these roles were, in fact, already experienced in government. This thesis also compares and contrasts the effectiveness of papal and secular measures in protecting the crusader's interests, and assesses the political impact of the crusaders' departure on those they left behind. Invasion, rebellion and usurpation could and did occur during the crusaders' long-term absence, but secular and papal protection might, in unison, combat exploitation by the crusaders' enemies or other opportunists.